Over 40 - over the Hill?

A friend of mine with a huge following posted the top under 40 HR bloggers today on their site. Interesting that lists are now segmented to age brackets, or maybe relevance.
Not sure if being over 40 is relevant in the social media space these days, yes face book and linkedIn certainly have a large over 40 user base, but from a posting perspective there is certainly a question of credibility.
I always thought wisdom and experience had a larger value....makes one think about the the future of social media...